This invention relates to a phenolic fraction of a group of compounds present in olive plants known as hydroxytyrosol (3,4-dihydroxyphenylethanol). Particularly, the invention provides an olive extract containing hydroxytyrosol, with low amounts or substantially free of oleoeuropein and tyrosol, and a method of obtaining the same.
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A high amount of dietary fat has been implicated in the development of several diseases (Owen et al., 2000c). Atherosclerosis (Kuller, 1997) and coronary heart disease (Gerber, 1994), as well as cancer of the breast (La Vecchia et al., 1998), prostate (Chan et al., 1998), ovary (Risch et al., 1994), and colon (Armstrong and Doll, 1975) have each been associated with elevated dietary fat. However, evidence indicates that it is not only the amount, but also the type of dietary fat that is important in the etiology of some cancers (Bartsch et al., 1999).
Olive oil, the principal fat component of the Mediterranean diet, has been associated with a lower incidence of coronary heart disease (Owen et al., 2000b; Parthasarathy et al., 1990; Mattson and Grundy, 1985) and certain cancers (d""Amicis and Farchi, 1999; Braga et al., 1998; Martin-Moreno et al., 1994). Several laboratories have reported that the hydrolysis of the olive oil phenolics oleuropin and other family members lead to small phenolic components with strong chemoprotective activity (Owen et al., 2000a; Manna et al., 2000). In particular, the olive oil phenolic hydroxytyrosol prevents low density lipoprotein (LDL) oxidation (Visioli and Galli, 1998), platelet aggregation (Petroni et al., 1995), and inhibits 5- and 12-lipoxygenases (de la Puerta et al., 1999; Kohyama et al., 1997). Hydroxytyrosol has also been found to exert an inhibitory effect on peroxynitrite dependent DNA base modification and tyrosine nitration (Deiana et al., 1999), and it counteracts cytotoxicity induced by reactive oxygen species in various human cellular systems (Manna et al., 2000). Finally, studies have shown that hydroxytyrosol is dose-dependently absorbed in humans following ingestion, indicating its bioavailability (Visioli et al, 2000).
Conventionally, olive oil production involves crushing olives, including the pits, to produce a thick paste. During this procedure, the crushed olives are continuously washed with water, a process known as xe2x80x9cmalaxation.xe2x80x9d The paste is then mechanically pressed to squeeze out the oil content. In addition to providing olive oil, the pressing also squeezes out the paste""s water content. Such washing and pressing steps yield a considerable amount of water, referred to as xe2x80x9cvegetation water.xe2x80x9d
Both the pit and the pulp of olives are rich in water-soluble, phenolic compounds. Such compounds are extracted from olives during malaxation, according to their partition coefficients, and end up in the vegetation water. This explains why various phenolic compounds, such as oleoeuropein and its derivatives, produced in olive pulp, can be found in abundance in vegetation waters. Similarly, a number of monophenolic compounds, such as tyrosol and its derivatives, produced in olive pits, are also abundant in vegetation waters.
Because of the strong chemoprotective activity of hydroxytyrosol, it is desirable to develop a method which produces an aqueous olive extract with a high percentage of hydroxytyrosol.
In one aspect, the invention includes a method of producing a hydroxytyrosol-rich composition. The method has the steps of (a) producing vegetation water from olives, preferably depitted olive meat, (b) adding acid to the vegetation water in an amount effective to produce a pH between 1 and 5, preferably 2-4, and (c) incubating the acidified vegetation water for a period of at least two months, typically 6-12 months until at least 75%, and preferably at least 90% of the oleoeuropein originally present in the vegetation water has been converted to hydroxytyrosol.
In one embodiment, the incubating is carried out until the vegetation water has a weight ratio of hydroxytyrosol to oleoeuropein of between 5:1 and 200:1, preferably 10:1 and 100:1. In a related embodiment, the incubating is carried out until the vegetation water has a weight ratio of hydroxytyrosol and tyrosol of between 3:1 and 50:1, typically 5:1 to 30:1.
The method may further include fractionating the incubated, vegetation water to separate hydroxytyrosol from other components, and/or drying the vegetation water of isolated hydroxytyrosol to produce a dried extract.
In another aspect, the invention includes a method of producing a hydroxytyrosol-rich composition that includes the steps of (a) producing vegetation water from olives; (b) optionally, drying the vegetation water; (c) contacting the optionally dried vegetation water with a supercritical fluid; and (d) recovering the hydroxytyrosol-rich composition from the contacted vegetation water. In one embodiment, the hydroxytyrosol-rich composition includes at least about 95 percent by weight hydroxytyrosol. In another embodiment, the hydroxytyrosol-rich composition includes at least about 97 percent by weight hydroxytyrosol. In yet another embodiment, the hydroxytyrosol-rich composition includes at least about 99 percent by weight hydroxytyrosol.
In one embodiment, the recovering step described above includes the steps of (a) recovering the supercritical fluid, where the supercritical fluid contains the hydroxytyrosol; and (b) vaporizing the supercritical fluid to extract the hydroxytyrosol-rich composition. In another embodiment, the contacting step described above comprises the steps of (a) providing a porous membrane having opposite sides in a module under pressure with the membrane serving as a barrier interface between a fluid and a dense gas, the membrane being nonselective for said hydroxytyrosol; (b) providing the supercritical fluid into the module on one side of the membrane and the vegetation water on the opposite side of the membrane; (c) and extracting the hydroxytyrosol across the membrane as driven by a concentration gradient of the hydroxytyrosol between the vegetation water and the supercritical fluid. In one embodiment, the porous membrane is a hollow fiber membrane. In another embodiment, the supercritical fluid is carbon dioxide.
In another aspect, the invention includes a dietary supplement comprising an aqueous extract of olives containing a weight ratio of hydroxytyrosol to oleoeuropein of between 5:1 and 200:1, typically 10:1 and 100:1.
In a related aspect the invention includes a dietary supplement comprising an aqueous extract of olives containing a weight ratio of hydroxytyrosol and tyrosol of between 3:1 and 50:1, typically 5:1 and 30:1.
The above supplements may be dried to provide a powder extract, which can formulated into a tablet, capsule, pill, or confection food additive.
These and other objects and features of the invention will be more fully appreciated when the following detailed description of the invention is read in conjunction with the accompanying figure and tables.